I think one part of the "Page Designer" is quite unfamiliar even to experienced APEX developers.

It is the "Grid Layout". Even I still struggle getting used to this new feature.
For that I will give you a small example how to read the new grid.
Maybe some of you have seen my example application about RaphaelJS.

I migrated this application into the new APEX 5 EA. Btw: No issues occurred.

What you see are three regions. The one above is including a select item and below are the other two beside each other. One is showing the harbor (report-view on the left) and the other one is showing the detail mask (on the right).

Inside the new "Page Designer" it looks like this:

You can see all three regions including all detail elements in each region.

To make it even more clear I put both views together:

What you see on the left is a shortened version of the "Pager Designer Grid View", surrounded with different rectangles to show the different regions and arrows showing to the right. There you see the application marked with the belonged rectangles.
Maybe you have seen that the button area on the left is shortened because of lack of space. But this example makes one thing clear. You need a big screen to not get the wrong perspective on the new "Grid View". For that I propose a curved 34" monitor. ;)

Sure it is not easy getting used to the new "Grid View" but on the other side if you are new to APEX it will be a really handy tool to learn and build even faster. :)